(i) Field of the Invention
This invention relates to mooring lines and systems and more particularly to an anchoring and mooring system for a drillship.
(II) Description of the Prior Art
The drilling of oil and gas wells in water covered Arctic regions have made it necessary to use a floating vessel called a drillship, usually one containing a vertical opening called a moonpool in the midsection thereof through which drilling operations are conducted. During the drilling operations, it is necessary that the moonpool stay at approximately a fixed position. Thus, to hold a floating drillship in position during drilling operations in marine locations, particularly in the Arctic areas, it has been the practice to use a plurality of mooring lines, each connected at one end to a spaced-apart location on the drillship and at the other end to an anchor. One such system of mooring included eight mooring lines, i.e., two each fore and aft, port and starboard sides. Each of the mooring lines was controlled by a tension winch, and included a length of chain or cable connecting the winch to the anchor.
While such mooring line system is generally satisfactory, there are certain conditions, for example, ice intrusion into the drilling area, where it is desirable and necessary quickly to move the drillship off the drilling location. Relocation of the moonpool of the drillship precisely over the drilling area therefore becomes a problem, since it is necessary to reconnect the mooring lines or cables to the drillship when the drillship is returned to its original location.
One manner of solving such problem which has been suggested involved the use of a spar buoy mooring system allowing a manual but rapid release and a manual reconnect of the mooring line.